Is there a fundamental acceleration?

Summary

The accelerationa ₀∼10⁻⁸ cm s⁻² appears insistently in physics and seems to play a fundamental role at the cosmological, astrophysical and microphysical level. It is the surface gravity of all mesons, of a typical protostar, of a typical galaxy and of the entire Universe; it is also the minimal acceleration an electric charge must have to radiate, the minimal centripetal acceleration of the quarks trapped in a spinning meson, the minimal acceleration a frame must have to feel the Unruh temperature, the minimal value a gravitational field must have to induce transitions between states of opposite parity in the hydrogen atom, the acceleration of any particle of rest massh/Rc (R= the radius of the observable Universe) such as the graviton; from the existence of the fundamental accelerationa ₀ one can derive the Weinberg relation (connecting microphysics to cosmology) and the well-known rough equality (so far unexplained) between the energy density of the cosmological microwave radiation, of the mean galactic magnetic field, and of the starlight in the Milky Way.